1. Field of the Invention
The present invention relates to a method of delivering data such as image data, and more particularly to a data delivery method that is capable of specifying a data receiver and verifying a range of received data.
The present invention also relates to a storage medium having stored software for executing a data delivery method such as the above-mentioned.
2. Description of the Related Art
A system for delivering digital image data to many and unspecified users via a public line network is known. This system has been expected in a system whose efficiency is good for both an image provider and a user.
A so-called electronic distributed press, which takes advantage of such a system and delivers through a network a printed publication hitherto distributed through the medium of paper, has also been viewed as an important method. Especially, the case of electrically performing the delivery of advertisements and catalogues of goods and printing them at a general user's home has been viewed as an excellent advertising medium in place of direct mail, because information can be provided only for a user who desires to have the information, without waste and a provider can also collect latent customer information.
Incidentally, although the cost of generating such commercially distributed goods should be originally charged to an information provider side, in the existing circumstances the communication expense of accessing data, expendable supply expense for printing, electric expense and the like will be all charged to a user. This fact has resulted in the cause of the obstruction of the spread of the above-mentioned excellent information delivery system.
In contrast to this, it has also been considered that information printing expense is cashed back to a user side, for example, by causing a user to input his or her ID in down-loading an advertisement page. In that case, however, there is no means of confirming that printing was actually performed, this fact constituting an obstacle to the spread of the system.
On the other hand, as indicated in Japanese Unexamined Patent Publication No. 9(1997)-191394 and Paper for The Institute of Electronics, Information and Communication Engineers, D-2, Vol. J80-d-2 No. 5, 1997, a method of embedding into digital image data the related information as “an electronic watermark” has been proposed. This electronic watermark is embedded into data as deep auxiliary information such that it is not recognized by ordinary human sense, when data embedded with the watermark is used for its original purpose. That is, for example, the information, which is embedded in image data, is embedded, for example, into a signal component corresponding to an extremely high space frequency so that the contents of the deep auxiliary information are not visually recognized, when the image data is used to reproduce an image.
If this electronic watermark technique is utilized, auxiliary information can be embedded inseparably from image data that is contents. Therefore, it is possible to set information so that it cannot be taken out, unless all image data is actually downloaded. From the fact that information has been taken out, it can be verified that advertisement data has been fully accessed.
However, if the taken information is embedded into another image and delivered, fraudulent utilization such as substitution of advertisement data will become possible. In addition, a fraudulent demand for payment becomes possible by delivering a copy of extracted data to someone else. Thus, there is a possibility that a variety of problems will arise.
From such points, a method capable of reliably proving the downloading of advertisement and propaganda page data at a client side has been desired.
While the aforementioned has been described with relation to problems with delivery of image data, the same demand is also present for the case where voice data, representing music and the like, and the other data are delivered to many and unspecified users.